Threaded fasteners are one of the most common mechanical fastening systems in use today. While bolts and nuts are typically the primary threaded fasteners, screws are just as common and important in the construction of mechanisms consumers use in multitudes of ways every day. A screw is used when, instead of a work piece being clamped between a nut and the head of the fastener, a portion of the work piece is internally threaded and the screw is torqued into the work piece itself. As with all threaded fasteners, screws torqued into engagement with an internally threaded work piece are subject to loosening over time and, as with threaded nuts and bolts, numerous devices have been incorporated to prevent such loosening. In other applications of screws being torqued into a work piece, vibration or dilation will also cause the screw to loosen over time. Often these screws are located in areas that are difficult to access, or may even be totally inaccessible to being re-tightened.
In the particular case of eyeglasses, the screws securing the temples and lenses often loosen, followed by the undesired consequence of a temple falling off or a lens falling out. The causes of such loosening in eyewear are varied. The repeated opening and closing of the temples by rotating the temple about the screw retaining it to the frame of the glasses will induce rotational loosening. Thermal gradients in the environment have a more pronounced effect on the female thread in which the screw is received than on the male threaded screw thus resulting in additional loosening forces.
In other applications of screws being torqued into a work piece, vibration or dilation will also cause the screw to loosen over time. Often these screws are located in areas that are difficult to access, or may even be totally inaccessible to being retightened.
Prior attempts to overcome these loosening forces have included the addition of a smaller setscrew, or locking screw, that is threaded through the side of the work piece into interfering perpendicular contact with the threads of the screw. However, a locking screw is subject to the same loosening forces as the primary screw and can be difficult and expensive to install. Additionally, in the case when the primary screw is relatively small, adding a setscrew becomes impractical. Various types of liquid metal on metal glues have been utilized, but over time the effectiveness of these substances is questionable. Lock washers also have mixed success results.
Other attempts to prevent loosening have included the use of lock washers, but these generally provide unsatisfactory results in situations of considerable vibration. Castellated nuts and cotter pins inserted through holes drilled in the bolt, have also been utilized to prevent loosening of the nut, and are generally successful in so doing, but the cost of installation is high and labor intensive. Screw and nut ensembles having movable locking assemblies have also been used; while they are generally effective, their cost is high.
Further, a problem encountered with machine screws not typically found with regular nuts and bolts is that a machine screw will often engage a greater number of threads in the work piece than in a standard nut of the same size or, in other cases, will require a screw of a significant threaded length necessitating numerous revolutions of the threads to reach a final torqued position. Mechanical locking systems incorporating deformed threads to interferingly lock the fastener in place become disadvantageous in these circumstances. With long threaded fasteners or numerous internal threads engaged by the fastener, the significant number of turns required to finally torque the fastener will either totally defeat the deformation feature by the time final torquing is accomplished or the extended sustained torquing force applied to the fastener head will often damage the head making a final torquing impossible and requiring an undesired replacement.
In the case of container having a closure consisting of a threaded collar and cap and containing carbonated or other beverages, pressure may build up in the container, and the container may also be subject to rough usage; thus a rather long collar and cap thread is required to assure engagement of a significant number of cooperating threads, to assure that the cap is well secured on the container collar; thus, many revolutions of the cap are required to reseal the container. Often, however, users simply neglect to “tighten” the cap to full closure to reseal the container properly or, even if the cap had been tightly screwed onto the collar, it may loosen—resulting in a container losing carbonation and/or leaking its contents, with the attendant consequences. A definite consumer advantage would accrue if the container cap could come to a secure full-closure position rapidly, without a significant number of revolutions, and be prevented from loosening from that position.
There are many types of pipe and tube fittings, the principal one among them being threaded fittings. Such fittings are required to maintain in a fully torqued position at least two elements of a piped or tubing assembly. Speed of assembly of such threaded fittings to a fully torqued position is always an issue and, often, such fittings and assemblies are subject to vibrational stresses, which cause a fitting to loosen, and the transported material to leak thereat. A definite industrial advantage would accrue if the tubes' or pipes' threaded fitting elements could come to a secure fully-torqued position rapidly, without a significant number of revolutions, and be prevented from loosening from that position.
Thread engagement must be discussed when discussing threaded locking fasteners. It is well known that manufacturing variations in common nuts and bolts create an ensemble wherein only relatively few threads of a common nut threaded on a common bolt are in effective mutual engagement. Obviously, the locking features of the device disclosed herein would be vitiated if most, if not all, of the threads of the male and female parts herein disclosed were not in effective engagement. It is therefore preferable that the screw and female receiver disclosed herein be manufactured to specifications adequate to assure effective engagement of their threads, as a set. Obviously, in the case of a threaded container closure, that is always the situation. In the case of tube or pipe fittings and assemblies, especially where the transported material is critical, no leakage is desired, such that the male threaded part and the female receiver disclosed herein be manufactured to specifications adequate to assure effective engagement of their threads, as a set.
Thread pitch is also a consideration to be weighed in applications using the configuration disclosed herein. It is obvious that, the higher the thread pitch of the configuration, the more rapid is the clamping action provided by the ensemble. The choice of thread pitch has no influence on the efficacy of the configurations disclosed herein.
Thus, what is desired is a mechanism for quickly positioning and locking screws torqued into a threaded hole in a work piece and wherein the mechanism will reliably maintain the desired engagement of the screw in the receiving hole throughout the life of the apparatus on which it is installed.